FIG. 1 (Prior Art) is a diagram of a conventional microcontroller motor drive circuit. System 10 comprises a power supply 11, a microcontroller 12, three half-bridge driver integrated circuits 13-15, three high-side driver transistors 16-18, three low-side driver transistors 19-21, and a three-winding motor 22. The half-bridge driver integrated circuits 13-15 are standard commercially available integrated circuits. Each half-bridge driver integrated circuit may, for example, be an IR2153 self-oscillating half-bridge driver circuit available from International Rectifier, 101 N. Sepulveda Blvd., El Segundo, Calif. 90245. The high-side driver transistors 16-18 and low-side driver transistors 19-21 are common, commercially available, external discrete N-channel Field Effect Transistors (NFET).
In operation, the power supply 11 supplies a high-voltage supply voltage (for example, approximately +170 VDC or +325 VDC depending on an input voltage source) via conductor 23 to the half-bridge driver integrated circuits 13-15 and to the high-side driver transistors 16-18 as illustrated. The power supply 11 also outputs a lower voltage DC supply voltage to power the microcontroller 12. The microcontroller 12 supplies control signals to the integrated circuits 13-15 so that certain high-side drivers (not shown) and certain low-side drivers (not shown) in the integrated circuits 13-15 will control certain of the external discrete NFETs 16-21 to be on and others of the NFETs to be off. By appropriate control of which ones of the NFETs 16-21 are on and off, a drive current can be made to flow into the motor 22, through a selected first winding of the motor 22, through a selected second winding of the motor 22, and out of the motor 22. As the motor 22 operates, the microcontroller 12 controls which pairs of motor windings receive the drive current so that the motor 22 is driven correctly.